Engine Vacuum Issues - 72 Automatic with 350 Base Motor

[Terry M.]

Re: Engine Vacuum Issues - 72 Automatic with 350 Base Motor

I have an issue with vacuum on my 72 vette. We sorted out the brakes and electrical gremlins and the car finally fired up after three years. This is the good news. The bad news is despite being perfectly timed, the vacuum is very low and clearly we have some issues despite replaced all of the lines for the headlights and wipers - basically everything that is vacuum operated was replaced. We have one large vacuum leak that despite numerous attempts at resolving I can't fix. The carburetor to intake manifold leaks on the right side of the carb. The carb was professional restored and it works beautifully, the carb base is not warped nor is the intake manifold base. What can I do to stop the vacuum leak on the base of the carburetor? Once i sort that out i can go through the system, but the leak is so bad i cannot drive the car under its own power.

Christopher,
Apparently no one else has a 1972 AIM. Too bad.
My 1972 AIM that is in the house is missing the requisite carburetor torque page, so I will have to quote from the 1971 AIM. BTW: You really should have your own copy of the 1972 AIM. And now you will see why.

UPC 6 Sheet C1 for 1971 shows this note for carburetor torque:
"TORQUE SEQUENCE
Torque bolt C & nut D to no. 1 (24-48 LBS IN) torque
Bolt E & nut F to no. 1 (24-48 LBS IN) torque
Re-torque C & D, E & F in the same sequence to no. 3 (120-168 LBS IN) torque
NOTE: A residual torque of 75 lbs in. minimum must be maintained after roll test."

Bolt C is the driver’s side front and nut D is passenger rear. E & F are the opposite.

All that kind of makes one think they regarded the carburetor tightening pretty important, eh?

BTW: The part between the carburetor and the intake manifold is called an INSULATOR and # 3982944 is shown for 1971.

You will have to wait until I can get to my garage library to find the equivalent 1972 page. That will take me a while.

[Christopher R.]

Re: Engine Vacuum Issues - 72 Automatic with 350 Base Motor

Thanks for the advice, I will check hat this weekend with the new gasket and report back to the everyone